LIQUID CONNECTIVE TISSUE

These are those connective tissues which circulate throughout the body and transport various metabolites. They have following features:

1. Have common matrix called plasma.

2. Have various types of cells called corpuscles.

3. Fibres are not found in plasma.

4. Matrix is not formed by the cells itself.

Basically they are of three types :

1. Blood

2. Lymph

3. C.S.F.

BLOOD

Various features of blood are-

1. It is a liquid connective tissue.

2. It constitutes 9% of total body mass in adults. It is about 90 ml per kg of body weight in man and 65 ml per kg of body weight in woman.

3. Specific gravity - 1.060

4. pH: 7.33 - 7.41 (average 7.4)

5. Osmotic pressure at room temperature -7.6 atmosphere

6. Plasma - 55% by volume

7. Haemoglobin - Upto 14.5 gm/100 ml, average is 14-16 gm/100 ml.

Components of blood:

1. Plasma

2. Corpuscles.

Plasma: It is about 5% by body weight. It is pale yellow in colour, transparent and clear fluid. Only water contents of plasma are about 90-92% by volume; remaining 8-10% are other inorganic and organic substances.

Inorganic constituents: They are chiefly salts of sodium, potassium and various gases in dissolved state viz. -O2, CO2 and N2 etc.

Corpuscles:

(1) Red blood corpuscles: They are non-nucleated biconcave discs of diameter ranging from 6-9  with an average of 7.5 . The haemoglobin is the main solid which constitutes about 31-33% and is distributed in the stroma or meshwork of protein and lipids. Concentration of R.B.C. is about 52,00,000 ± 3,00,000 in man and 47,00,000 ± 3,00,000 in woman. Upto 13 years of age, number of R.B.C. in both sex is same. Inside the R.B.C. K' and MgH ions are present.

Production:

(1) In embryonic stage chief organ of production is liver and other are spleen and lymph nodes.

(2) Upto the age of 20 years, they are produced in the bone marrow of long bones.

(3) After the age of 20 years they are produced in the bone marrow of membranous bones.

(4) R.B.C. are derived by hymocytoblast or primordial stem cell or committed stem cell or unipotential stem cell. In the process of formation while the cells are at reticulocyte stage, they are squeezed into the blood capillaries. This phenomenon is called diapedesis.
(2) White blood corpuscles: They are mobile units of body defence system. They are formed partially in bone marrow [granulocytes, lymphocytes (few), monocytes] and partially in lymph tissue (plasma cells and lymphocytes). Average concentration of W.B.C. is 7000 per cubic mm of blood. Differential concentration is-

Polymorphonuclear neutrophills -62%

Potyrnorpnonuclear eosinophills -2.3%

Polymorphonuclear basophills -0.4%

Monocytes - 5.3%

Lymphocytes - 30%

Concentration of platelets is about 3,00,000.

Act of destroying foreign particles by W.B.C. is done by the phenomenon of phagocytosis. The word phagocytosis was given by Metchnikoff.

LYMPH

Lymph is like blood but having no R.B.C. and is colourless. It has normally more W.B.C. specially lymphocytes. Other components of blood in lymph are far less in quantity. It has ability to issue coagulate like blood. Daily production of lymph in human being is about 1 to 2 litres. The albumin/globulin ratio in lymph is much higher than plasma. Because protein contents are very low, it shows Donnan effect. Protein contents are highest in the lymphatics of liver and lowest in subcutaneous lymphatics.

Functions of blood and lymph:

1. Transport of nutrients like glucose, fatty acid, amino acid, glycerol, fructose etc. from gastro-intestinal tract to the various parts of body.

3. Transport of hormones from their site of production to the target organ.

4. Transport of gases i.e. O2 from lungs to tissues and CO2 from tissues to lungs.

5. Blood is an efficient buffer system in which various proteins act as buffer. They maintain overall pH of blood and the body.

6. By virtue of colloidal pressure of plasma fluid, balance of body is maintained. This exchange of water between blood and tissues is done via lymph.

7. Due to the constant circulation and specific heat of water, blood maintains body temperature.

8. Because blood and lymph are having various types of W.B.C., they actually participate in active defence mechanism of body by releasing various types of Iymphocytes/monocytes and antibodies.

9. Because blood is having clotting properties, it prevents haemorrhage. It is a self preservation mechanism.

CEREBROSPINAL FLUID (C.S.F.)

It is formed by choroid plexus and secreted into the lateral ventricles of brain, from where it is transported to other ventricles via sub-arachnoid space. It is about 5 ml in newly born and 100 to 150 ml in adult.

C.S.F. is considered to be ultra filtrate of plasma. Its pH is same as of plasma.

Composition:

Glucose (100 ml)

Urea nitrogen (100 ml)

Protein (100 ml)

Na, K. Mg. Ca. CI-. HCO•, etc.

Bilirubin (100 ml)

pH 55-80 mg

6-23 mg

20-40 mg

293 to 318 mg/litre

0

7.4

Main function of C.S.F. is to provide a protective jacket around brain and spinal cord. It is also nutritional and excretory in function.